In recent years, high-speed printing of direct mails or the like has been performed using inkjet printing apparatuses. With such printing apparatuses, an individual piece of information (so-called variable information) is printed on a portion of printing paper that corresponds to each page, the printing paper being roll paper. In images printed by the inkjet printing apparatuses (hereinafter referred to as “printed images”), ink dripping due to the heads of the printing apparatuses rubbing against printing media, or dot missing due to nozzle clogging may occur. Accordingly, an inspection apparatus for detecting such a defect is installed in the printing apparatuses. For example, in the case of color printing, the inspection apparatuses capture a printed image with a color line camera and detect a defect based on the captured image.
Furthermore, there are cases in which printing apparatuses print information elements such as characters, numbers, bar codes, or two-dimensional codes that represent character information or numerical information. Thus, it has been proposed to inspect these information elements in a printed image. For example, Japanese Patent Application Laid-Open No. 2006-79571 discloses a technique in which text printed on paper is recognized, decoded, and converted into a character code and then compared and checked against a character code to be printed, so that it is determined whether the printed text is acceptable or not. In an image recognition apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-277676, three verification fields on paper on which a telephone number or the like has been printed are captured with three OCR (optical character reader) cameras so that it is determined whether print quality is acceptable or not.
In recent years, there is demand for simultaneous inspections of a printed color image and printed information. In such a case, if an inexpensive color line camera that has a low line rate is used in an inspection apparatus, the imaging range taken in a single imaging operation on a fast-moving printing medium is expanded, and the captured image will appear in a state of being compressed in the direction of movement of the printing medium. As a result, for example, if the printed image includes a one-dimensional bar code in which bars are aligned in the direction of movement of the printing medium, the captured one-dimensional bar code will appear in a state in which adjacent bars overlap one another into a single bar, and thus decoding processing cannot be performed. If, as a countermeasure to this, a high-speed monochrome line camera unit that includes an illumination system is provided for decoding processing, separately from the unit used in color image inspection, the size of the inspection apparatus increases and inlining becomes difficult.